Honestly, I have not expected much from this book. Biodiversity or ocean acidification are not really my cup of tea. At least, they weren’t until now. The book is a real page-turner. It reads like an eco-thriller. I’ve read it faster than the science-fiction “The Ministry For The Future” by Kim Stanley Robinson.
“The Sixth Extinction” is a compelling and sobering exploration of the current state of our planet's biodiversity. Kolbert takes readers on a journey through time, science, and history to shed light on the ongoing mass extinction event, laying bare the undeniable fact that we are the primary culprits behind this catastrophe. I am writing a review of this book for two reasons. First, I outline the main takeaways for me and keep them handy for my work. Second, I want to show, why it is an essential read for anyone concerned about the future of our planet.
What are mass extinctions?
Before we delve into the book's core arguments, it's crucial to understand what mass extinction is. Curiously enough, Ms. Kolbert points out that “Extinction may be the first scientific idea that kids today have to grapple with”. When playing with plastic dinosaurs, our kids soon understand and can explain to us that these are very big creatures, that lived long ago and have all died. The concept of mass extinctions first emerged in France in the 18th century and the idea that a catastrophe might have caused it was floated in the 19th century - “The word “catastrophist” was coined in 1832 by William Whewell, one of the first presidents of the Geological Society of London, who also bequeathed to English “anode,” “cathode,” “ion,” and “scientist.” In the 20th century, the term “mass extinction” was finally articulated by the American paleontologist David M. Raup only in the 1960s.
Mass extinction is defined as an event in which a significant portion of Earth's species is wiped out in a geologically short period of time, leading to a profound shift in the planet's biodiversity. The five previous mass extinctions in Earth's history have left a lasting mark on the planet's biodiversity and habitat. Let's briefly examine them.
The first mass extinction, known as the Ordovician-Silurian extinction, occurred around 440 million years ago and was driven by glaciation and cooling temperatures, leading to the loss of many marine species and their habitats.
The second major event, the Late Devonian extinction roughly 360 million years ago, was attributed to a combination of factors, including sea-level changes and the spread of anoxic conditions in oceans, which severely affected marine life and their habitats.
The third mass extinction, the Permian-Triassic extinction, often referred to as the "Great Dying," took place around 250 million years ago. It was the most catastrophic, resulting in the loss of over 95% of marine species and nearly 70% of terrestrial species. This event was primarily driven by volcanic activity, which led to extreme climate changes and habitat destruction. Ocean acidification also played a major role in this catastrophic event.
The fourth mass extinction, the Triassic-Jurassic extinction, approximately 200 million years ago, saw the loss of many marine and terrestrial species. It was linked to volcanic activity and changes in sea levels, disrupting habitats on a global scale.
The fifth mass extinction, the Cretaceous-Paleogene extinction, took place around 66 million years ago and is perhaps the most famous due to the extinction of non-avian dinosaurs. This event was triggered by the impact of a massive asteroid, which caused catastrophic fires and a "nuclear winter" effect, drastically altering habitats worldwide. The story of the scientific discovery of this event reads like a techno-thriller.
In each of these mass extinctions, the loss of habitat played a pivotal role. Environmental changes, driven by natural phenomena, drastically altered ecosystems. The speed of the change denied the organisms any chance to evolve to match new habitats. The speed I am talking about is measured in hundreds of thousands of years. This was not enough time for the organisms to evolve and adapt to new conditions, so they just, well, went extinct. The Earth's habitats were transformed, and it took millions of years for new ones to emerge.
Why We Are in the Middle of a Mass Extinction Event?
Ms. Kolbert presents a compelling case for the ongoing mass extinction event by diving deep into several cases of animal and insect extinctions. She discusses the dramatic decline in populations of various species, ranging from frogs to bats, and cites research that indicates we are in the midst of a major biodiversity crisis: “It is estimated that one-third of all reef-building corals, a third of all freshwater mollusks, a third of sharks and rays, a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are headed toward oblivion.”
Plants are not immune to this crisis either. Kolbert's book shows how we are losing plant species at an unprecedented rate, and this often goes unnoticed. These extinctions can disrupt ecosystems and have cascading effects on other species, including humans.
Why This Extinction is Anthropogenic?
Kolbert's central argument is that the 6th extinction is primarily anthropogenic, meaning it is caused by human activities. She presents a compelling case by examining how we have altered the planet's ecosystems through deforestation, pollution, overfishing, and greenhouse gas emissions. Her position is clear: we are the driving force behind this crisis.
The ways in which humans drive other species extinct are numerous. Starting with the straightforward mass killing of great auks, to a less proven disappearance of the American mastodon, which was strangely coincidental with the spread of modern humans, to less well-known cases like deforestation of Easter Island, which was not caused by humans, but by rats, that humans brought with them.
Ever more subtle are the effects of pumping CO2 and other GHG gases into the atmosphere. About a third of all emissions are absorbed by the oceans, but gases dissolved in the oceans are then again released into the atmosphere. When the two are in balance, everything is fine, but as more and more GHG gases are pumped into the atmosphere, more get into the oceans and they start to change.
“Ocean acidification is sometimes referred to as global warming’s “equally evil twin”. There is a mind-blowing chapter in the book, that describes in vivid detail how a more acidic ocean makes it difficult for creatures with shells or exoskeletons to build them. Acidification also leads to changes in the amount of light, that passes through water, and this in turn may lead growth of toxic algae.
In "The 6th Extinction," Elizabeth Kolbert provides a meticulously researched and thought-provoking account of the mass extinction event unfolding before our eyes. Her narrative skillfully weaves together science, history, and storytelling to make a compelling case that we are the architects of this crisis. This book serves as a crucial wake-up call, urging us to recognize our role in the ongoing extinction event and take immediate action to safeguard the future of our planet and all the species that call it home. It's a must-read for anyone concerned about the environment and the fate of life on Earth.